1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device in which a plurality of semiconductor elements are arranged and, more particularly, it relates to a method of separating semiconductor elements.
2. Description of the Prior Art
In general, separation between semiconductor elements in such a semiconductor device was performed by a selective oxidation process. However, in such a process, there inevitably arose intrusion of an oxide film into active regions, i.e., so-called bird's beak, and unevenness of the surface caused by swelling of the circumferential portion of the oxide film, i.e., so-called bird's head. The former restricted high density integration of the semiconductor device, while the latter caused inconvenience in multilayer interconnection for the high density integration.
To avoid these disadvantages, a selective epitaxial growth process has been proposed for use in forming such a semiconductor device, in which an insulating layer formed on a substrate is selectively removed and a semiconductor layer is then selectively epitaxially grown on the removed portions. However, the semiconductor layer obtained through the epitaxial growth process also has the disadvantage of unevenness of the surface similar to the oxide film obtained by the selective oxidation process.
In order to overcome the aforementioned disadvantages of the prior art, a method of manufacturing a semiconductor device was proposed in which flatness of the semiconductor device comprising a plurality of semiconductor elements is improved, thereby enabling further effective high density integration. More specifically, according to the proposed method, portions of an insulating film formed on a substrate are selectively removed, whereafter flatness of semiconductor layers on the removed portions, which has not been obtained by conventional selective epitaxial growth under atmospheric pressure, is readily realized by selective epitaxial growth under reduced pressure. Selectivity for epitaxial growth is also improved by the above proposed process, so that the growth of semiconductor on the insulating film is effectively reduced. The selective silicon epitaxy at low pressure for providing good selectivity and flatness is described by S. Hine et al in the proceedings of the Fall Meeting of Japan Society of Applied Physics, October, 1981, page 747. Semiconductor elements are formed in the semiconductor layers thus obtained. However, it was observed that there is still room for improvement of the flatness and selectivity of the semiconductor layers obtained by the selective epitaxial growth under reduced pressure.